China is the biggest foreign owner of Treasury debt and had appealed to U.S. leaders to protect its $1.1 billion in holdings during last week’s debate over raising Washington’s borrowing limit and avoiding a possible default.

In a statement, Zhou Xiaochuan welcomed the deal by American leaders to raise the limit but also called for Washington to avoid further steps that might hurt investors.

“Large fluctuations and uncertainties in this market would undermine the stability of the international financial system and hinder global recovery,” Zhou said. The central bank took the unusual step of posting his comments in both English and Chinese on its website, clearly aiming to reach a foreign audience.

Treasury debt is among the most widely held assets and often is used as the benchmark for interest rates on commercial credit. Any changes due to uncertainty about U.S. finances could have global repercussions by pushing up borrowing costs.

“China hopes the U.S. administration and the Congress would take responsible policy measures to handle its debt issue in light with the interests of the whole world including those of the United States,” Zhou said.

He gave no details of possible measures China wants to see.

The statement came after President Barack Obama signed legislation Tuesday to raise Washington’s $14.3 trillion borrowing limit just hours before a midnight deadline.

Beijing is believed to be diversifying its foreign currency reserves but Treasurys are expected to remain a big part of its portfolio. Few other asset markets are big enough to absorb the tens of billions of dollars China’s central bank adds to its reserves each year.

Also Wednesday, a Chinese rating agency said it has downgraded Washington’s credit rating from A+ to A.

The move by Dagong Global Credit Rating Co., which is little-known abroad, is unlikely to affect U.S. borrowing rates but reflects the pessimism Washington’s debt battle has generated worldwide.

Dagong said the debt deal doesn’t change the fact that U.S. debt growth has outpaced its economy and fiscal revenue. It warned earlier of a possible downgrade if the United States didn’t show it had the ability and willingness to repay its debt.